In order to properly understand this AU you must study Latvian mythology extensively as all the monsters in this AU represents the mythos of Latvia. But please understand that the information you see here is changed to fit the AU and my personal understanding of my cultures mythology and so it may not reflect on the correct descriptions of said mythos.
This au has three Sanses that can conjoin into one. All three are mainly gods of faith. But seperately they represent these concepts of life - Birth, Luck, Order. Early in life they were female, and anatomically they still are, but they transitioned into looking more male overtime, and now also prefer male pronouns and terminology.
Sans (Birth): "Dēkla" or Dekla Sans, the Protector of newborns and cattle, and the all knowing of pregnancy and everything dealing with bringing life. His objects - a swaddle and a dagger. He was pregnant early in his life but lost the child due to them being a mortals child and he hates his counterparts because of their cold reactions to his suffering. He knows that he can't do anything about their judgement but still blames them for not trying anything to change fate.
Sans (Order): "Kārta" or Karta Sans, the Writer of every living beings lifepath, what he writes is permanent and not even Dievs (Asgore) can change this. His objects - book and feather and a lidded watch of all possibilities on a chain.
Sans (Luck): "Laima" Sans, the strongest of the trio, deals with all aspects of life - living, marriage and dying. He protects homes and families, gives hope in war, and kills unquestioningly when noone else will, his judgement is final above all else. His objects - a simple straw broom, it may seem insignificant but it can be transformed into any other object of his choice, from medicine to sword, but in the end it is called "Broom of judgement" for a very good reason. He also dislikes chaos and dirty surroundings, keen to bringing bad fate to those who don't try to get their surroundings clean and in order (aka basic hygiene).
All three of them seperately are at the power level of Reapertale Sans and Toriel (both because all three of them deal with both life and death at the same time). Their fusion, called Laima Sans or Trīdeksnis (Trīdeksnis is a type of musical instrument and the "Trī" part sounds alot like "Three" so hense the namechoice), is three times stronger than them. Their fusion doesn't have a specific object, all they have to do to decide the fate of any living being is taking a step in one or the other direction, taking a step to the right meaning that they are letting you live and vice versa. If you have the misfortune of meeting this fusion then your fate is no longer yours, but theirs, all you have left is hope at that point. Pretty much just dont piss off Latviantale Sanses to this point or you are dead no matter what you do. Their fusion however cannot override the power of Sanses that possess any powers related to overriding judgement or Sanses that are stronger than them, Dreamtale brothers and parasite Sanses are also unfortunately not in their grasp. Pronouns of the fusion: They/He/She.
Other significant characters:
There are two Papyruses, Jumis and Ūsiņš (Usin), gods of harvest and cattle, they helped Dekla Sans with his birth, raising the baby with him through the short time the child could live and then helped him through his loss. Noone else helped Dekla and they were the only ones qualified enough for such matters even though at the time it was extremely frowned upon for men to deal with female matters. They also dislike Karta and Laima but also do not question the two's judgement. (Pronouns for both: He/Him)
Alphys is Nāve, the goddess of death, particularly - helping souls through the journey to afterlife. Typically this goddess wears white and is seen dancing or hanging out on graves (Pronouns: She/Her) Previously this title belonged to someone who.. never existed.
Undyne is Pērkons, goddess of thunder, typically a male god. She inherited this status from Gerson (God of War) who was her mentor before passing on. (Pronouns: She/Her)
Asgore is Dievs or "God", though he is entirely unrelated to the christian God, he also holds less power than the Sanses. (Pronouns: He/Him)
Toriel is Māra or something similar to mother Mary, esentially mother of all mothers and Dievs wife. (Pronouns: She/Her)
Flowey is Vadātājs, aka a evil being that will try their best to confuse you until you die. Essentially if you're in a forest and you realise that you have been walking in circles for hours then you have for sure encountered this being. Their entire purpose is to tire you out or kill you without you ever seeing them (as in, falling off a cliff or something else like that). (Pronouns: it/it's)
Frisk and Chara are Tautubērni, in this AU Frisk is a girl and Chara is a boy. Historically Latvian culture is very gendered, to the point where we don't have a third pronoun, so this fact is included in this AU just to make it more culturally accurate. Tautubērni are mortals.
I don't remember what Metatton and Asriel were supposed to be, so I'll add this information when I remember it.
Also ghosts in this AU are called Veļi.
The clothes represent latvian native costumes and clothes, and the cultural significance behind every accessory is taken into consideration as well.
